Observations on the distensibility of the common bile duct.

This series describes 9 patients in whom a rapid change in bile duct caliber was documented by ultrasonography, intravenous or direct cholangiography, or endoscopic retrograde cholangiopancreatography. Two major observations were made: (a) the capacity of the common duct to distend and collapse over a short period, and (b) discordant measurements of bile duct diameter on successive examinations with different modalities (i.e., ultrasonography followed by cholangiography). It is thought that these discrepant measurements can be explained by the ability of the common duct to distend rapidly in response to pathologic and physiologic fluctuations in biliary pressure.